"Scantily clad" girls as young as 13 are being rejected from high school dances for wearing "basically nothing" and some schools fear parents are unaware of the rebellious behaviour.

Year 9 and 10 "sock-hops" in Christchurch are attracting "explicit" female outfits, such as mini dresses made of "Danger Keep Out" tape, spandex hot pants, crop tops and even boys' underwear.

Supervisors have reported seeing girls climb out of taxis and shed layers upon arrival, and one dance-goer said "bundles of clothes" were shoved into the corners of the girls' toilets after being discarded inside.

Some schools scrapped the 13- to 15-year-old social events a few years ago blaming a spate of "unruly behaviour", while others have tried to muzzle the disorder with breathalysers at the door and supervisors scrutinising each outfit.

One year 9 girl who was denied entry to this month's Christchurch Boys' High School (CBHS) dance said it was "really embarrassing" when a parent supervisor told her and a friend to: "Go put more clothes on."

The pair had decided to dress as superheroes and were wearing black spandex shorts with rolled up singlets, showing off their painted stomachs. They were both able to enter the dance when they rolled their singlets back down, she said.

Another year 9 pupil said she knew of five girls who had been rejected from the CBHS dance, including two who had wrapped themselves in "Danger Keep Out" tape.

Christchurch Girls' High School decided to cut its junior dances about seven years ago due to "unacceptable behaviour", principal Prue Taylor said.

She had been "appalled" when she heard pupils had been turning up intoxicated and said the revealing outfits and "rowdiness in the streets" that followed the dance had cemented the school's decision.

CBHS principal Trevor McIntyre believed the girls were "much more covered up" now than they used to be and said the dances had evolved into fancy dress, with many girls arriving as cats, lions and fairies.

'SEXY AND THEY KNOW IT'

A Canterbury University academic says the young girls donning explicit outfits for junior dances are under the influence of pop stars such as Lady Gaga.